The present invention relates to an optical wave network system by means of a wavelength multiplex technique in optical communication or optical exchange, and more particularly to a network trouble monitoring method for efficiently providing multimedia service by constructing an economical and pliable network, and an optical communication or optical exchange system utilizing the method.
A wavelength division multiplexing (WDM) method is a transmission method for multiplexing and transmitting signal light having a number of different carrier optical wavelengths in one optical fiber, and is a technique that is useful for increase of transmission capacity. In a conventional network equipped for management, maintenance and control thereof, there is one optical wavelength of a signal transmitted in an optical fiber. In this case, with regard to monitoring of a trouble or quality deterioration of an optical transmission line, meaning monitoring the disconnection or deterioration of an optical signal for every wavelength of an optical signal, a method based on a time division multiplexing (TDM) method is utilized, and is constructed in accordance with a method defined by GR253-CORE of the Bellcore standard, for example. Particularly, main signals are contained in standardized transmission frames that are partitioned with respect to time, and information for network control is added to the signals as a frame overhead in accordance with a standardized format. In each network element, monitoring of a trouble or quality deterioration of an optical transmission line is conducted by analyzing or renewing this overhead information.
In recent years, a demand for multimedia service that requires several M(mega)b/s bands has rapidly increased, and a necessity of enlarging communication capacity of individual service has occurred. In addition to this, a transmission system that can be efficiently adapted to various transmission speeds or formats such as a video image, voice and data is earnestly desired.
In the case of providing service by using a new synchronous network, it is necessary that, by means of a time multiplexing method, the service is mapped into a frame of a transmission speed or a format provided by the new synchronous network and is transmitted between points. Unless that multimedia service having various transmission speeds is always mapped into a fixed frame, the frame or network has to be reconstructed in accordance with a demand that continuously changes. In the case that the transmission is conducted by using frames of 1.5 Mb/s, 50 Mb/s and 150 Mb/s, for example, when the service provided between points changes such that voice (64 Kb/s) changes to a dynamic image (64 Mb/s) and voice (64 Kb/s), an interface transfer with the 1.5 Mb/s frame, the 50 Mb/s frame and the 150 Mb/s frame has to be conducted many times. Also, at the same time, since it is necessary that the frame overhead information for the network control is renewed at any time, the control is complicated. Moreover, in order to enlarge the transmission capacity, it is necessary to newly define a format of the frame and conduct standardization.
Namely, from a controllability and flexibility standpoint, it is said that the monitoring of a trouble or quality of the optical transmission line in accordance with the new synchronous network is unsuitable for a network that handles various formats and transmission speeds. Although it becomes possible to multiply and contain a plurality of optical channels in one optical fiber, the monitoring of a trouble or quality deterioration of the optical transmission line using a wavelength multiplexing technique is not defined in the conventional method of monitoring a trouble or quality deterioration of the optical transmission line.
Therefore, in order to efficiently provide multimedia service for which demand is rapidly increasing, it must be taken into account that the communication capacity occupied per service is large and that the signal formats vary, and that these tendencies will be greater in the future. In order to construct a flexible and highly reliable service transfer network, it is necessary to realize a method of monitoring a trouble or quality deterioration of an optical transmission line, which is suitable for a wavelength multiplexing optical network.
Therefore, the objective of the present invention is to solve the above task, and to provide an optical wave network system capable of monitoring a trouble or quality deterioration of an optical transmission line in transmission of various service data and of transferring trouble information.
Another objective of the present invention is to provide an optical wave network system capable of monitoring a trouble or quality deterioration of an optical transmission line in transmission of various service data and of transferring trouble information, which is suitable for a change of a transmission speed of a transmission signal and a signal format.
The objective of the present invention is to provide an optical wave network system capable of simplifying network control, in which even though the contents of a service demand continuous change, it is not necessary to follow the change of the contents of the service demand and conduct an interface transfer of a transmission signal with respect to time.
Yet another objective of the present invention is to provide an optical wave network system capable of economically and pliably handling multimedia service of which communication capacity per service is large and which has various formats and transmission speeds.
In order to achieve the above-described objectives, an optical wave network system of the present invention is an optical network system utilizing a wavelength or spatial multiplexing technique in which optical fibers are physical media. The optical wave network system includes a plurality of optical signal terminal stations, and optical network elements connected to the above-described optical fibers for forming wavelength paths between the above-described optical signal terminal stations, and monitors a trouble or quality deterioration of physical path connection and transfers a trouble alarm through the optical network elements for every wavelength path without depending on a transmission speed or format contained in the wavelength paths, and in case that a trouble or quality deterioration of optical signals occurs in the wavelength paths, physically recovers this network trouble by performing a quick failure recovery by means of the above-described optical network elements from the wavelength paths of a using system to predetermined exclusive wavelength paths of a spare system.
Also, in the protection by the above-described wavelength paths of a spare system of the present invention, a method can be adopted, which is constructed to perform a quick failure recovery by retrieving wavelength paths of a spare system that is not in use and is shared in a network.
In the above-described optical wave network system of the present invention, the optical fibers constitute a plurality of transmission lines between optical network elements, of which transmission directions of signals are different, and can be constructed so that wavelength paths having one or more than one different carrier wavelength transmission directions, in the direction of the signals, are formed by wavelength multiplexing, and the above-described wavelength paths can be constructed so as to include virtual wavelength paths which are formed by conducting at least one wavelength conversion between wavelength path terminal ends by means of the above-described optical network elements. A wavelength conversion means that the wavelength 1 of an optical signal, for example, is converted into the wavelength 2, without changing the optical signal information about the wavelength 1. Moreover, the above-described optical network elements can include optical ADMs and optical cross-connect systems, and the above-described optical ADMs or optical cross-connect systems can be constructed so as to have a function for physically reconstructing a network by reconstructing wavelength path connecting condition.
Furthermore, the monitoring of the trouble or quality deterioration of the physical path connection and the transfer of the trouble alarm for every wavelength path in the above-described optical wave network system of the present invention can be conducted by means of average optical power of the above-described optical signals or amplitude of the optical signals.
More particularly, the optical wave network system in accordance with the present invention is an optical network system utilizing a wavelength or spatial multiplexing technique. The optical wave network system at least includes optical signal terminal stations, and includes one or more than one optical network elements of at least one or more than one kinds of optical cross-connect systems or optical ADMs that are optical network elements, or optical regenerative relay amplifiers. And, the optical wave network system monitors a trouble or quality deterioration of physical path connection and transfers a trouble alarm through the optical network elements for every wavelength path or virtual wavelength path without depending on a transmission speed or format contained in the wavelength paths or the virtual wavelength paths, and has a high speed network trouble recovery function for physically conducting protection by quickly recovering the failure at high speed by means of the optical network elements from the wavelength paths or virtual wavelength paths of a using system to predetermined exclusive wavelength paths or virtual wavelength paths of a spare system, or for conducting protection by retrieving wavelength paths or virtual wavelength paths of a spare system that is out of use and is shared in a network, in case that a trouble or quality deterioration occurs in the wavelength paths or the virtual wavelength paths. Also, the optical wave network system has a function for physically reconstructing the network by reconstructing a wavelength path connecting condition in case of receiving a demand, and has a function for conducting long distance optical communication in which optical fibers are physical media by applying wavelength multiplexing to the wavelength paths having at least one or more than one different carrier wavelength directions, in the direction of the transmission, and, if necessary, by conducting at least optical regenerative relay amplification and wavelength distributed control for every wavelength path, and thereby, the optical wave network system has a high speed trouble recovery function in addition to the flexible and economical handling of the service of arbitrary transmission speed or format for every wavelength path or virtual wavelength path.
In the optical layer using a wavelength or spatial multiplexing technique, services are allocated for every wavelength path in which communication channels between points are allocated to each wavelength. Thereby, it is possible to conduct communication that does not depend on a signal transmission speed or format between points connected to each other without reconstructing the network or conducting an interface transfer with respect to time. In other words, if the terminal end points are not changed, it is not necessary to physically reconstruct the network or conduct an interface transfer with respect to time service by service, even though signals to be transmitted are continuously changed to signals having various transmission speeds and formats, such as a video image, voice and data.
Therefore, it is not necessary to reconstruct the network or conduct an interface transfer with respect to time every time the transmission speed is changed, and it is possible to simplify the control. Also, it is not necessary to conduct standardization of signal formats for increasing the transmission speed. Moreover, it is possible to economically conduct the signal transmission by utilizing the wide band characteristic of light.
Also, in the optical layer, a physical network trouble recovery function can be realized by monitoring a trouble or quality deterioration of an optical transmission line at a unit of the wavelength paths. In this monitoring of the wavelength paths, an arrangement of an efficient network function can be realized by conducting the monitoring by means of network elements such as an optical cross-connect system and an optical add drop multiplexer (referred to as an xe2x80x9cADMxe2x80x9d) which has a function for reconstructing the wavelength paths in the optical layer. Also, by utilizing optical average power in a method of monitoring the wavelength paths, high speed monitoring that does not depend on a transmission speed or format can be easily realized by means of a simple apparatus arrangement.